Humpback whale calf in between 10-16 feet (3-4.5 meters) in length and can weigh up to one ton (907kg). Mother-calf pairs have the strongest and most lasting bond within humpback whales. The calf will stay with its mother for about a year until it is weaned. During that time, it will feed on a fat rich milk to put on weight very quickly and be able to migrate to the feeding grounds with its mother.